The conformational analysis of a series of phenyl 2,3,6-tri-O-benzyl-β-D-thio galacto-and glucopyranosides and their 6S-deuterio isotopomers, with systematic variation of the protecting group at the 4-position, will be described. The phenyl 2,3,6-tri-O-benzyl-β-D-thio-galacto and glucopyranosides show small and systematic changes in the side chain conformation on changing the functionality at the 4-position from a hydroxyl group to an ether and to an ester. To study the effect of side chain conformation on oxocarbenium ions, the galacto-configured azasugars such as isofagomine, 1-deoxynojirimycin derivatives, and their trifluoroacetate salts were prepared. Derivatives of galacto-configured 1-deoxynojirimycin reveal change in the least populated gauche, gauche conformation but a large increase in the gauche, trans conformation that stabilizes positive charge on going from the neutral to the protonated form. In the isofagomine series both 4-O-ethers and esters show an increase in the positive charge stabilizing gauche, gauche conformation on protonation.

Interplay of protecting groups and side chain conformation in glycopyranosides and azasugars as models for glycosylation reactions

2019 Spring National Meeting

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